The conic generator invention disclosed herein is employed as a subsystem in the video generator circuit for a dynamic digital television display disclosed in U.S. Pat. application 478816, A. A. Schwartz, and W. J. Hogan, filed 6/11/74 and assigned to the instant assignee. This video generator circuit system converts randomly occurring data signals representing graphical patterns into a time sequential video signal for use with a sequentially line scanned display device. The circuit is comprised of a threaded buffer connected to receive the data signals and adapted to sort the data signals into groups ordered by extremal scan line positions for the pattern represented. An intermediate buffer has a first input connected to the output of the threaded refresh buffer for storing the ordered data signals once during each display field before the display of the pattern represented and outputting the ordered data signals in synchronism with the line scans of the display. A graphical pattern generator is connected to the output of the intermediate buffer for decoding the ordered data signals outputted therefrom and generating on a first output line components of the pattern represented which lie along the display line to be scanned. A partial raster assembly storage is connected to the first output line from the graphical pattern generator, to store the components of the pattern represented which lie along the display line to be scanned. The graphical pattern generator modifies the decoded ordered data signals to identify the horizontal coordinate for the intersection of the pattern represented with the next display line to be scanned, and outputs the modified data signal over a second output line to a second input line for storage in the intermediate buffer. The graphical pattern generator omits the output of a modified data signal on the second output line when no components of the pattern will intersect succeeding display lines to be scanned in the field.
Prior art digital conic generators have employed recursive techniques to incrementally generate a conic section to be displayed one element at a time. Although this may be suited to random plotters, this mode of generation is not suitable to raster-type devices since the generation time for the conic section is proportional to the number of elements which fall on a raster line. What the art requires is an improved conic shape generator which generates all of the elements on each raster line at a single time and would, therefore, be amenable to high speed television display.